Field of the Invention
The invention generally relates to mobile communication networks. Particularly, the invention relates to intersystem mobility security context handling between different radio access networks.
Description of the Related Art
There exist a variety of different data communication systems or networks. Each network has its own characteristics and specifications. When there exists several different networks, there is always a problem of how to interconnect these networks, i.e. how to execute a switchover or handover of a connection from one network to another.
GSM EDGE Radio Access Network (GERAN) is the radio part of GSM/EDGE together with the network that joins the base stations The network represents the core of a GSM network, through which phone calls and packet data are routed from and to the PSTN and Internet to and from subscriber handsets.
UMTS Terrestrial Radio Access Network (UTRAN) is a collective term for the Node B's and Radio Network Controllers which make up the UMTS radio access network. The UTRANs is able to carry many traffic types from real-time Circuit Switched to IP based Packet Switched. The UTRAN contains base stations, which are called Node Bs, and Radio Network Controllers (RNC). The RNC provides control functionalities for one or more Node Bs.
Evolved UTRAN (E-UTRAN) is an evolution of the 3G UMTS radio access network towards a high-data-rate, low-latency and packet-optimized radio-access network.
In E-UTRAN user equipment (UE) can have both a mapped and cached security context during mobility from GERAN/UTRAN to E-UTRAN. In the mapped security context EPS (Evolved Packet System) keys and other security parameters are converted from received context from UTRAN/GERAN. In the cached security context EPS keys and other security parameters are cached in the EPS and re-used when UE moves to the EPS system, e.g. from UTRAN/GERAN or WiMAX/WLAN/DSL.
One of the problems in idle mode mobility or handover to/from E-UTRAN is that how does both user equipment and E-UTRAN negotiate key usage in the different cases when the user equipment has or does not have the cached security context or when E-UTRAN has or does not have the cached security context.